Dennis Mersereau

A frustrating bureaucratic technicality led to a confusing situation this afternoon as a thunderstorm straddling state lines prompted the issuance of one of the most ridiculous-looking tornado warnings ever seen. The inconsistency has a good reason behind it, but these types of quirks can hurt public trust in weather forecasts.

The National Weather Service is broken up into 122 Weather Forecast Offices (WFOs) around the 50 United States and its territories. Each WFO is responsible for a certain number of counties around the vicinity of the office. Some forecast offices cover vast expanses of land (such as NWS Albuquerque, covering most of New Mexico) while others, such as NWS Huntsville, cover a relatively small area.

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The intersection of borders that delineate the coverage area for each office (or "area of responsibility) are often a source for incongruity among weather forecasts. One of the most visible cases where forecasts between two offices don't mesh well along the edge of their areas of responsibility are snowfall forecasts. There was a notable case this past winter where the NWS in Binghamton, New York disagreed with the office in Buffalo about how much snow would fall, so it left a nasty divide in forecasts across the Finger Lakes; totals jumped from 8-10" to 18-24" across county lines.

This disagreement between forecasters at different offices is also seen in severe weather warnings, and especially the tornado warning along the Ohio/Kentucky border this afternoon.

NWS Wilmington, Ohio issued a tornado warning for a storm that had weak rotation in it for Lewis County, Kentucky and Scioto County, Ohio around noon Eastern Time. Due to state lines following the curvature of the Ohio River, Scioto County nestles Greenup County, Kentucky in sort of an arcing shape, leaving Greenup County bordered by Ohio on three sides.

The path of the storm took it over Lewis, Scioto, and Greenup Counties, but no tornado warning was ever issued for Greenup County, leaving a strange arcing polygon that seems to defy physics and logic.

Greenup County didn't go under a tornado warning because it's under the responsibility of a different NWS office in Charleston, West Virginia.

The fact that the rotating thunderstorm crossed between the Wilmington and Charleston areas of responsibility caused the incongruity. The forecaster responsible for issuing warnings at the Wilmington, Ohio this afternoon thought that the rotation in the thunderstorm was enough of a threat to issue a tornado warning, while the forecaster in charge of warnings in Charleston, West Virginia disagreed.

The end result was a confusing mess of polygons along the path of the storm. Charleston ultimately decided to issue a severe thunderstorm warning to fill the gap, and (thankfully) there were no reports of damage from this particular storm.

Forecasters don't always agree with each other. Regardless of how much objective data you have, the ultimate practice of weather forecasting is subjective. It comes down to the forecaster's knowledge and biases. Unfortunately, when subjectivity and bureaucracy mix as they did today, it can lead to a confusing situation for the public, and one that could hurt public trust in the future.